Phylloxera conica

(Shimer, 1869)

hickory phylloxeran, hickory phylloxera

Phylloxera conica is a gall-forming insect closely related to aphids that induces distinctive globular galls on hickory leaves and petioles. The insect overwinters as on bark or near old galls, with nymphs emerging during bud break to feed on new growth. Their feeding stimulates abnormal plant development, creating hollow galls that provide shelter and food. The has a complex involving multiple , with winged forms eventually dispersing to lay eggs. Heavy can reduce tree vigor and nut production in hickory trees.

Pronunciation

How to pronounce Phylloxera conica: //fɪˈlɒksərə ˈkɒnɪkə//

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Identification

Distinguished from other phylloxera by its association with hickory (Carya spp.) rather than grape or pecan. The globular galls on hickory leaves and petioles are characteristic; pecan phylloxera (Phylloxera devastatrix) attacks pecan shoots and nuts, while grape phylloxera (Daktulosphaira vitifoliae) affects grapevines. The galls of P. conica are typically found on mockernut hickory and other hickory species, not on oak or elm where other gall-forming insects occur.

Habitat

Deciduous forests and landscapes containing hickory trees, particularly mockernut hickory (Carya tomentosa) and other Carya . Found in areas with mature hickory trees where can survive on bark and previous gall sites.

Distribution

Eastern North America, where hickory trees are native; documented in regions including the northeastern and midwestern United States based on tree distribution.

Seasonality

hatch during spring bud break; galls develop through late spring and early summer; galls split open by late May to release winged ; eggs laid by mated females in late season.

Diet

Feeds on phloem sap of hickory leaves using ; nymphs feed within galls on plant tissue stimulated by their secretions.

Host Associations

Carya tomentosa - primary mockernut hickory
Carya spp. - various hickory

Life Cycle

Overwinters as on bark crevices or near old galls. Eggs hatch at bud break into fundatrix nymphs that induce gall formation on new leaves and petioles. Each fundatrix develops into a mature female that lays hundreds to over a thousand eggs parthenogenetically within the gall. These eggs hatch into nymphs that feed and develop into winged forms. Galls split open by late May, releasing winged that move to leaf undersurfaces to lay eggs producing sexual males and females. After mating, females lay eggs that complete the cycle.

Behavior

Nymphs secrete chemical substances that manipulate plant , causing abnormal differentiation and gall formation. The insect remains enclosed within the gall during most of its development, protected from and environmental conditions. Winged disperse relatively short distances to new feeding sites.

Ecological Role

Acts as a gall-forming herbivore that can reduce hickory tree vigor and nut production during heavy . Galls provide microhabitats for other organisms; the insect itself serves as prey for . Nutrient-rich gall tissue may be consumed by wildlife.

Human Relevance

Considered a minor pest of hickory trees in natural and landscape settings; can reduce aesthetic value of ornamental hickories and potentially impact nut production for wildlife. No significant commercial pest status compared to related grape phylloxera. Control rarely needed in natural settings.

Similar Taxa

Phylloxera devastatrixAlso in Phylloxeridae but attacks pecan rather than hickory; induces galls on pecan shoots and nuts rather than leaves
Daktulosphaira vitifoliaeGrape phylloxera, historically devastating to vineyards; different specificity and gall on grapevines
Phylloxera caryaecaulisAnother hickory-feeding phylloxera with similar and gall-forming habit on hickory

More Details

Gall chemistry

Research by Glen Hood and colleagues has demonstrated that insect-induced galls like those of phylloxera can accumulate soil contaminants at higher concentrations than surrounding plant tissues, suggesting potential use as pollution bioindicators.

Taxonomic note

Some sources list this under the Daktulosphaira as D. conicum, reflecting ongoing taxonomic revisions within Phylloxeridae.